Inorganic fillers or pigment powders generally have a relatively high density and a surface in a polar state, which naturally settles in water. The organic surface modification is a water-insoluble surfactant or a coupling agent. Therefore, the surface-modified inorganic powder (pigment or filler) has a surface that changes from polar to non-polar, which is more pronounced for water. Strong non-invasive. This non-wetting fine particles, in the water, are so floating as the oil film due to the large surface tension.
According to this phenomenon, the concept of " activation index " is proposed , which is represented by H, and its meaning is expressed by the following formula:
H = mass of the floating part of the sample (g) / total mass of the sample (g) 
â–² The point A of the abscissa corresponding to point a in the curve is the amount of surface modifier forming a monomolecular coating on the surface of the inorganic filler or pigment, which can be used as the optimum amount of surface modifier. However, in actual treatment, it should be slightly lower than this amount.
It can be seen from the above figure that the inorganic powder not treated by surface activation (ie, modification), H=0; when the activation treatment is the most complete, H=1.0 (100%); the change process of H from 0-1.0 can reflect The degree of surface activation of the powder is from small to large, that is, the degree of surface organic treatment is good or bad.
In the organic surface modification process of inorganic fillers or pigments, the variety and amount of surface modifiers have a significant effect on the performance of the filling system. The amount of surface modifier can be determined by reference to the "activation index" .
The optimal amount , that is , the amount of the surface modifier on the surface of the filler or pigment particles, covering the monolayer, above this amount, a multi-layer physical adsorption interface weak layer will be formed, thereby causing the strength of the filler to decrease; Below the optimum dosage, the surface treatment of the filler particles is incomplete, which is reflected in the variation curve of the “activation index†H. As the amount of the surface modifier increases, the initial stage H increases, and H rises from 0 to 1.0. No longer change.
It should be noted that the activation index cannot be used as the sole quality indicator for powder surface modified products . On the one hand, after modification with different surface modifiers, the activation index may be different, but it does not mean that the higher the activation index, the better the surface modification effect, and should be combined with other indicators such as adsorption type (chemical adsorption or physics). Adsorption), the role of the polymer binder and the application performance indicators are considered together.
â– Example: Determination of calcium carbonate activation
Determination of the degree of activation in GB/T 19281-2014 Calcium Carbonate Analysis Method.
(1) Method summary
The degree of surface coating of calcium carbonate was determined by the characteristics of hydrophobicity after surface treatment of calcium carbonate.
(2) Instrument
Separating funnel: 250mL
Glass mortar: filter plate aperture 5-15μm
Electrothermal constant temperature drying oven: temperature can be controlled at 105 °C ± 2 °C
(3) Analysis steps
Approximately 5 g of the sample was weighed to the nearest 0.01 g. It was placed in a separatory funnel, and 200 mL of water was added thereto, and shaken at a speed of 120 times/min for 1 minute. Place gently on the funnel holder and let stand for 20min-30min. After the stratification was apparent, the sinking calcium carbonate was once put into a glass mortar which was previously dried at 105 ° C ± 2 ° C to a constant mass, and the water was removed by suction filtration. It was placed in an electric oven and dried at 105 °C ± 2 °C until the mass was constant.
(4) Calculation of results
The degree of activation is calculated by mass fraction H and is calculated as follows:
In the formula:
m 2 is the value of the mass of the dried and uncoated calcium carbonate after drying, in grams (g);
m 1 is the mass of å©åŸš, in grams (g);
m is the value of the mass of the sample in grams (g).
The arithmetic mean of the parallel determination results is the measurement result, and the absolute difference of the parallel measurement results is in accordance with the product standard.
Self-Tapping Screw,Pan Head Self-Tapping Screw,Flat Self Tapping Screw,Round Head Self-Tapping Screw
Taizhou Fengye Metal Products Co., Ltd. , https://www.fyhandware.com